First, think about how Naruto's personality has changed over the years. Maybe he's more patient and less impulsive. Then, consider his relationships. For example, his relationship with Hinata might be different. You can start with a simple scenario like Naruto reflecting on his past adventures while sitting on his porch. And don't forget to add some new challenges for him in his old age, like a new type of enemy or a problem within the village.
Naruto would likely be devastated. His old team was an important part of his early life in the ninja world. He might initially go into a state of shock, unable to believe that they are gone. Then, his grief could turn into anger, vowing to find out who was responsible and make them pay.
Yes, there might be such fanfictions. Many fanfic writers like to explore different timelines and scenarios for their favorite characters. In a 'naruto is an old man' fanfic, Naruto could be having adventures that are different from his youth, perhaps mentoring the new generation with his years of wisdom.
Naruto's character development in this fanfiction is multi - faceted. Firstly, he becomes more empathetic. He has seen a lot since his early days and now he can truly feel what his old teammates are going through. When Sasuke is in danger, Naruto doesn't just rush in blindly. He assesses the situation and thinks about how Sasuke would want to be saved. Secondly, he becomes more self - assured. He doesn't doubt his abilities as much. This is because he has faced many challenges and overcome them. His relationship with Kakashi also evolves. He respects Kakashi even more but also can offer his own insights and suggestions. All these aspects of his character development are intertwined with his mission to save the old Team 7.
Naruto's experience in handling loss and grief can be of great value to Aang. Both have lost important people in their lives. Naruto can show Aang how to turn that pain into strength. By sharing his own journey of dealing with the death of his loved ones and still moving forward, Naruto can help Aang not be consumed by his own losses and instead use them to fuel his growth as the Avatar.
His old team would be Sasuke, Sakura, and Kakashi. They are the main characters associated with Naruto's early team experiences. In the context of this fanfic where they die, it's likely to have a huge impact on Naruto and the overall story.
I recommend the novel,"Reborn from the Fire: The Concubine's Daughter Yingluo" to you. This novel tells the story of the female protagonist who became the concubine's daughter Yingluo after her rebirth, but was sent to the nunnery to commit suicide. Later, she accidentally saved a few princes and her sister was reborn there. The story was compact and emotional. I recommend it to readers who like fantasy novels. I hope you like this fairy's recommendation. Muah ~😗